Bayesian estimation and selection of nonlinear vector error correction models: The case of the sugar-ethanol-oil nexus in Brazil

Nonlinear adjustment toward long-run price equilibrium relationships in the sugar-ethanol-oil nexus in Brazil is examined. We develop generalized bivariate error correction models that allow for cointegration between sugar, ethanol, and oil prices, where dynamic adjustments are potentially nonlinear functions of the disequilibrium errors. A range of models are estimated using Bayesian Monte Carlo Markov Chain algorithms and compared using Bayesian model selection methods. The results suggest that the long-run drivers of Brazilian sugar prices are oil prices and that there are nonlinearities in the adjustment processes of sugar and ethanol prices to oil price but linear adjustment between ethanol and sugar prices.

In vitro fermentation of sugar beet arabinan and arabino-oligosaccharides by the human gut microflora

Aims: To determine the fermentation profiles by human gut bacteria of arabino-oligosaccharides of varying degree of polymerization. Materials and Methods: Sugar beet arabinan was hydrolyzed with a commercial pectinase and eight fractions, of varying molecular weight, were isolated by gel-filtration chromatography. Hydrolysis fractions, arabinose, arabinan and fructo-oligosaccharides were fermented anaerobically by gut bacteria. Total bacteria, bifidobacteria, bacteroides, lactobacilli and the Clostridium perfringens/histolyticum sub. grp. were enumerated using fluorescent in situ hybridization. Results: Bifidobacteria were stimulated to different extents depending on molecular weight, i.e. maximum increase in bifidobacteria after 48 h was seen on the lower molecular weight fractions. Lactobacilli fluctuated depending on the initial inoculum levels. Bacteroides numbers varied according to fraction; arabinan, arabinose and higher oligosaccharides (degree of polymerization, dp > 8) resulted in significant increases at 24 h. Only carbohydrate mixtures with dp of 1-2 resulted in significant increases at 48 h (log 8.77 +/- 0.23). Clostridia decreased on all substrates. Conclusions: Arabino-oligosaccharides can be considered as potential prebiotics. Significance and Impact of the Study: Arabinan is widely available as it is a component of sugar beet pulp, a co-product from the sugar beet industry. Generation of prebiotic functionality from arabinan would represent significant added value to a renewable resource.

Biofuel policies in the EU, US and Brazil

The development of biofuels has been one of the most visible and controversial manifestations of the use of biomass for energy. Biofuels policies in the EU, US and Brazil have been particularly important for the development of the industry in these three important markets. All three have used a variety of measures, including consumption or use mandates, tax incentives and import protection to promote the production and use of biofuels. Despite this, it is uncertain whether the EU will achieve its objective of a 10 per cent share for renewables in transport fuels by 2020. The US is also running into difficulties in meeting consumption mandates for biofuels. Questions are being raised about the continuation of tax credits and import protection. Brazil has liberalised its domestic ethanol market and adopted a more market-oriented approach to biofuels policy, but the management of domestic petroleum prices and the inter-relationship between the sugar market and ethanol production are important factors affecting domestic consumption and exports. In both the EU and the US an ongoing debate about the benefits of reliance on biofuels derived from food crops and concern about the efficacy of current biofuels policies may put their future in doubt.